Voltage regulator circuits can serve numerous purposes in integrated circuit devices. One particular application can be to regulate an internal power supply voltage for certain sections of an integrated circuit device. Even more particularly, voltage regulators can supply a power supply voltage to memory cell arrays within memory devices, such as content addressable memories (CAMs), static random access memories (SRAMs) and dynamic RAMs (DRAMs), as but a few of the many possible applications.
Among the various types of voltage regulators are “shunt” type regulators. A typical shunt regulator provides a shunting current path from a load (i.e., the regulated node). When a voltage to the load exceeds a predetermined amount, the shunt path can be enabled, and typically, a large amount of current is diverted (shunted) from the load to prevent an overvoltage condition at the load.
One conventional shunt regulator is shown in U.S. Pat. No. 6,586,917 B1 issued to Gregory J. Smith on Jul. 1, 2003 (Smith). Smith teaches an arrangement in which a shunting device can be enabled in response to either of two feedback loops. The feedback loops both include fixed resistors that provide a voltage divider that provides an input voltage to an amplifier. When a voltage divider potential exceeds a given reference voltage, the amplifier enables the shunt device, which shunts current to ground until the feedback loop(s) indicates a regulator input or output has returned to a desired level.
While arrangements like that of Smith can provide appropriate current shunting for certain applications, such arrangements can be less suitable for other applications. In particular, in some applications it may be desirable to limit power consumption and/or current draw as much as possible. In approaches like Smith, there can be considerable power consumption at the high limit of an external power supply range, as each time the power supply voltage exceeds the regulation limit, by even a relatively small amount, the amplifier can drive the shunting device (e.g., transistor) into saturation, and large amounts of current can be shunted to ground. In addition, such periodic current draws can tax power supply current sourcing capabilities, which may already be strained in high current applications, such as CAM devices, as but one example.
In addition, approaches like that of Smith may provide insufficient response at higher frequencies (greater than 1 MHz). If a load capacitance is relatively low with respect to peak load current demands, a regulated node potential may jump well beyond a desired limit before current shunting brings the potential back to the desired level.
A voltage regulator utilizing a current conveyor is shown in U.S. patent application Ser. No. 10/965,445, filed on Oct. 14, 2004, and corresponding International Application PCT/US2004/043756, filed on Dec. 22, 2004, entitled REPLICA BIASED VOLTAGE REGULATOR by the present inventor Iulian Gradinariu.
In light of the above, it would be desirable to arrive at a shunt-type voltage regulator that does not suffer from the above drawbacks of conventional approaches. More particularly, it would be desirable to provide a shunt-type voltage regulator that can provide a regulated voltage at higher supply ranges without consuming relatively large amounts of current. Further, it would be desirable for such a voltage regulator to provide a better high frequency response than conventional arrangements like those described above.